Falling Water Films over a Ring Attached to a Vertical Cylinder : Flow Configuration and Film Thickness

抄録

This experimental study concerns falling water films on a vertical cylinder to which a ring with a squared cross section of 1.5 mm×1.5 mm is attached. Film flows near the ring were observed while varying the longitudinal distance to the ring from the water distributor outlet from x₀=100 to 1100 mm and with the film Reynolds number from Re=50 to 800. The flow configuration was remarkably changed with x₀ and Re, and they were classified into several groups. Using the needle contact method, longitudinal distributions of film thicknesses were measured near the ring for two typical ring positions. When the ring was at x₀=100 mm in the non-equilibrium flow region with very weak waves, the waves were amplified downstream of the ring and the flow attained an equilibrium not far from the ring. When the ring was at x₀=500 mm, in the equilibrium flow with disturbance waves, the film flow disturbed by the ring seemed to be restored to the level of the upstream one.